Aphid/Rust Outlook: Monitor Fields Regularly for
Pests and Diseases
The likelihood of aphids being a problem in 2008 is very low, say checkoff researchers. However, that doesn’t mean aphids will not be around, but their numbers may not reach the economic threshold. On what basis are researchers making their predictions? The answer is a checkoff monitoring program that uses suction traps to catch aphids as they migrate to wintering sites. In the fall of 2007, very few aphids were caught in all seven participating states.
“Farmers should continue to monitor soybean aphids even though predictions indicate that they won’t be a widespread problem this year,” says Dr. David Wright, Iowa Soybean Association director of contract research and strategic initiatives.
Dr. Christina DiFonzo, Michigan State University field crops entomologist, says that while numbers are low now, there is really no way to prevent soybean aphid outbreaks in the future.
“Outbreaks occur in certain years,” DiFonzo says. “Watch newsletters, scout fields and make management decisions field by field. Some years outbreaks happen, other years there aren’t any.”
Dr. David Ragsdale, University of Minnesota professor of entomology, echoes these sentiments.
“What an individual farmer can do is to monitor their field during the summer,” Ragsdale says. “Aphids move large distances and also on the wind.”
Soybean rust overwintered in several locations in the South, including Mexico. Although it is too early to determine the impact on Midwest soybean acres, scientists are paying close attention because spores from that area can easily be blown throughout the heart of our soybean-producing area.
According to Wright, the potential economic impact is unclear.
“Soybean rust has not yet had a major economic impact on the U.S. soybean crop,” Wright says. “However, each year since its discovery in Louisiana in 2004, rust has progressively moved further into our major soybean-producing areas.”
Last year, rust was confirmed in 14 Iowa counties and one Canadian province, which suggests it is gaining a foothold as a problematic disease of U.S. soybean production. Researchers and crop specialists continue to monitor soybean rust through the nation’s safety net, the Sentinel Plot System. Through this system, growers can see known rust locations in the United States by logging onto www.sbrusa.net.
Currently, Asian Soybean Rust has been found in Mexico, Texas, Louisiana, Florida and Alabama. Compared to last year, the results are about the same.
According Jim Marois, professor of plant pathology at the University of Florida, how much rust is found in the South indicates how much may move into the Midwest.
“We had a warm winter here,” Marois said. “We weren’t able to find any rust on kudzu in the panhandle the past few weeks, but we found some in central and south Florida.”
The kudzu vine, a plant which also hosts the soybean rust fungus, thrives in a warm and wet climate. According to Marois, the leaves on the kudzu are developing now, and it’s a wait-and-see period. However, Marois thinks the rust is going to overwinter as well as before, if not better, unless there is a late frost. The normal frost-free date is March 15 in the Florida panhandle.
Watch for updates at www.planthealth.info and NCSRP e-newsletters.
